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Nutrients | Free Full-Text | Plant-Based Diets for Cardiovascular Safety and Performance in Endurance Sports | HTML
https://www.mdpi.com/2072-6643/11/1/130/htm
Because plants are typically low in saturated fat and devoid of cholesterol, vegetarian diets reduce plasma lipid concentrations [18], leading to reduced viscosity. In a study comparing 48 individuals following vegetarian eating patterns and 41 matched controls, plasma viscosity, packed cell volume, and blood viscosity were lower in vegetarians, and the stricter the avoidance of animal products, the greater the observed differences [39]. Individuals excluding meats entirely had significantly lower blood viscosity, compared with those having occasional meat (less than once a week). These observations were initially identified as an explanation for the lower blood pressure and lower prevalence of hypertension that are commonly observed among those following vegetarian diets. However, reduced blood viscosity also improves tissue oxygenation, potentially improving athletic performance.
The higher the saturated fat intake, the greater the impairment of flow-mediated vasodilation [42].
Although meals rich in animal fats impair arterial compliance, some added oils may have similar short-term effects. A single-meal experiment using a carrot cake and a milk shake prepared with coconut oil (which is high in saturated fat) demonstrated impaired arterial compliance, compared with the same meal prepared with safflower oil (which is high in polyunsaturated fat) [43]. Studies using olive oil (rich in monounsaturated fat) have yielded mixed results—some showed an impairment of flow-mediated vasodilation, others did not [44,45,46]. Overall, these studies suggest that, while animal fats are particularly harmful for arterial flexibility, there is a benefit from meals prepared from vegetables, grains, legumes, and fruits, without animal products or added oils.
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When the production of reactive oxygen species exceeds the body’s ability to neutralize free radicals through endogenous and exogenous antioxidants, the result is called oxidative stress. At low levels, oxidative stress upregulates antioxidant defenses [49] and boosts the immune response [50]. However, free radical production that greatly exceeds the neutralizing ability of antioxidant defenses can result in damage to DNA (leading to mutations), to plasma lipids (leading to atherosclerosis), and to proteins (leading to cell damage and accelerated aging). Exercise-related oxidative stress can also lead to muscle fatigue, reduced athletic performance, and impaired recovery [51].
Compared with omnivores, people following vegan and vegetarian diets have increased antioxidant activity, due to higher intakes of vitamin C, vitamin E, beta-carotene, and other antioxidants [52], as well as to higher antioxidant enzyme production [53]. Researchers have also found potentially beneficial effects of specific antioxidant-rich foods on exercise outcomes, notably beets [54], allium vegetables (e.g., garlic, onions, and leeks) [55], and cherry juice [56].
A plant-based diet appears to be a helpful part of a strategy to reduce inflammation. In a 2017 meta-analysis of 18 prior studies, vegetarian diets consumed over a two-year period were shown to reduce serum concentrations of C-reactive protein (a marker of inflammation), suggesting an anti-inflammatory effect of plant-based foods [59]. The anti-inflammatory benefits of plant-based diets may stem from (1) their antioxidant content, (2) the absence of products that may be inflammatory or sensitizing, or (3) the absence of pro-inflammatory fats. A few studies have examined the possibility that specific foods with antioxidant activity (e.g., tart cherries [61], pomegranates [62], blueberries [63], blackcurrants [64], and watermelon [65]) may decrease post-exercise inflammation and facilitate recovery.
In the Adventist Health Study, individuals who ate meat at least once per week had a higher prevalence (49% and 43% higher prevalence for women and men, respectively) of degenerative arthritis and soft tissue disorders compared with individuals who avoided meat [68]
In individuals with rheumatoid arthritis, several studies have demonstrated that vegan and vegetarian diets reduce C-reactive protein, as well as both subjective and objective signs of arthritis [69,70,71,72,73]. A vegan diet has also been shown to have an anti-inflammatory effect (as evidenced by reductions in C-reactive protein) in patients with and without coronary artery disease
4. Conclusions
Plant-based diets play a key role in cardiovascular health, which is critical for endurance athletes. Specifically, these diets improve plasma lipid concentrations, blood pressure, body weight, and blood glucose control, and, as part of a healthful lifestyle, have been shown to reverse atherosclerosis. The possibility that such diets may also contribute to improved performance and accelerated recovery in endurance sports is raised by their effects on blood flow, body composition, antioxidant capacity, systemic inflammation, and glycogen storage. These attributes provide a scientific foundation for the increased use of plant-based diets by endurance athletes.